[PATCH] D83082: [Alignment][NFC] Use proper getter to retrieve alignment from ConstantInt and ConstantSDNode

[Sam Clegg via Phabricator via llvm-commits]

sbc100 added a comment.

In D83082#2132017 <https://reviews.llvm.org/D83082#2132017>, @jrtc27 wrote:

> In D83082#2131971 <https://reviews.llvm.org/D83082#2131971>, @sbc100 wrote:
>
> > This change seems to have broken one of our tests in emscripten.  I reduced it to this:
> >
> >   #include <stdlib.h>
> >   #include <assert.h>
> >  
> >   int main() {
> >     void * ptr = aligned_alloc(3, 64);
> >     assert(ptr == NULL);
> >     return 0;
> >   }
> >
>
>
> Yeah, this is testing DR 460's new (and accepted) requirements (previously it was undefined):
>
> > If the value of alignment is not a valid alignment supported by the implementation or the value of size is not an integral multiple of alignment the function shall fail by returning a null pointer.


Regardless of weather its defined or undefined behaviour I wouldn't expect the compiler to crash though right?  Clearly this is a compiler bug, right?

> I feel this should probably be handled specially (ie use align(1) or no alignment) in the Clang frontend? Though I wouldn't like to say how things change when you change it to:
> 
>   int align = 3;
>   void *ptr = aligned_alloc(align, 64);

Same crash happens with this code.

> For sufficiently obfuscated code I can imagine Clang not noticing but a later LLVM pass discovering the alignment is a constant and trying to set the attributes up as such.




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